National Cartographic Information Center (Continued) 
Kind of Data 
Topographic and Other Maps 
Location: The standard topographic map series covers the 
United States, Puerto Rico, Guam, American 
Samoa, and the Virgin Islands. Information 
concerning the coverage of special maps can be 
obtained from the National Cartographic Infor- 
mation Center (NCIC) or the index map of each 
individual state published by the USGS. 
Dates: All the maps are periodically revised and/or 
field checked by the USGS. 
Description of Data: Under its National Mapping Program, the USGS has 
produced multipurpose published maps and basic map data for a variety of 
cartographic data needs (see information given under Map Data Catalog, 
National Mapping Program). The published maps include a series of topographic 
maps, orthophotoquads, orthophotomaps, state maps, county maps, special maps, 
US maps, national park maps, and selected national atlas maps. 
The unit of survey for the standard topographic map is a quadrangle 
bounded by parallels of latitude and meridians of longitude. Quadrangles 
covering 7-1/2 min of latitude and longitude are published at the scale of 
1:24,000 (1 in. = 2,000 ft). Quadrangles covering 15 min of latitude and 
longitude are published at the scale of 1:62,500 (1 in. = approximately 
1 mile). The maps graphically present the natural and man-made features of 
the land surface, and the shape and elevation of the terrain are portrayed by 
contour lines. 
The standard orthophotoquad consists of an orthophotograph (a nearly 
distortion-free black and white rectified aerial photograph) or mosaic of 
orthophotographs in 7-1/2-min quadrangles. Orthophotoquads are useful as 
up-to-date companions to standard topographic maps or as interim maps for 
areas not previously mapped. Orthophotomaps are full-color versions of the 
topographic maps based on orthographs. 
The standard topographic maps are very useful to engineers. Information 
concerning other published maps can be obtained from the NCIC at the following 
address: 
National Cartographic Information Center 
US Geological Survey 
507 National Center 
Reston, VA 22092 
(703) 860-6045, FTS 928-6045 
Ordering Information: A map should be ordered by name, series, and 
state in which it is located. It is noted that 
each quadrangle is designated by the name of a 
city, town, or prominent natural feature. 
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